1. Field of the Invention
The present invention relates to a photosensitive resin having the performance of high sensitivity and high resolution, a photoresist based on the photosensitive resin, a pattern formed using the resist, a pattern forming method, a device (semiconductor device) or a mask for exposure fabricated by the pattern forming method.
2. Related Background Art
In recent years, microfabrication is advancing in semiconductor elements including integrated circuits, display elements, and so on, or in masks for exposure or the like, so that pattern linewidths tend to be decreased. Exposure light used for the microfabrication is light in the near ultraviolet to ultraviolet region, and the processing is carried out in the wavelength region of these light beams (600 to 300 nm). The decrease of linewidths, however, is now approaching the limit, and for further decrease of linewidth, using light of shorter wavelengths as the exposure light is attempted. The photolithography technology using the ArF excimer laser of the wavelength 193 nm or the KrF excimer laser of the wavelength 248 nm as an exposure light source is under development in recent years.
With this tendency toward the shorter wavelengths of the exposure light, required properties of resists are high transmittance to the exposure light and high resolution. Japanese Patent Application Laid-Open Nos. 5-80515 and 5-265212 disclose resists. Japanese Patent Application Laid-Open No. 5-80515 discloses a resist comprised of a copolymer of 2-substituted 2-norbornene and acrylate. There is, however, some concern over toxicity, because the 2-substituted 2-norbornene disclosed in the application has the cyano group (CN). The reason why the copolymer can undergo alkali development is that its side chains are subject to hydroxylation. Therefore, it has low solubility in alkali solution. Japanese Patent Application Laid-Open No. 5-265212 discloses the resist comprised of a copolymer having the adamantane skeleton in side chains. The copolymer disclosed in this application, however, also has low solubility in alkali solution in alkali development, because it is a high molecular weight compound.